fscheck will allow you to display all of the extents of a file:
<SEVEN> MPEXL.TELESUP:fscheck
FSCHECK, A.05.00. (C) Hewlett-Packard Co., 1987. All rights reserved.
fscheck: displayextents xl.pub.sys
SECT_ADDR SECTS_IN_EXTENT VOL_SET_INDEX FILE_SECT_OFFSET
-------- --------------- ------------- ----------------
$000B6090 2048 1 $00008800
$000B6890 2048 1 $00009000
...